miku86

Posted on Oct 28, 2019

Summary: Computer Science and Programming in Python - Part 01

#python #beginners #tutorial

Intro

On my path of Learning In Public, I try to learn as efficient as possible. The stuff has to fit my needs, but I don't want to waste time by binge-learning useless stuff.

Therefore I decided to have a look at Computer Science and Programming in Python.

I don't know if it is too easy for me, because I know most of the Computer Science stuff, but therefore I decided to use a course with Python, because I only new the basics of it. If it is too easy, I go faster.

Links

I created a list with all the links to the summary, the videos and the slides.

There is also a link to the github repo, I invite you to make a Pull Request if you see some typos.

Summary

01. Computation

Overview

computer performs calculations
calculations are built-in or defined by developer
computer only knows what you tell it
types of knowledge:
- declarative: statements of facts
- imperative: recipe how to do sth
recipe (= algorithm)
1. sequence of (simple) steps
2. flow of control that specifies when each step is executed
3. a means of determining when to stop
fixed program computer: calculator
stored program computer: machine stores and executes instructions
basic machine architecture:
- input
- memory
- cpu (control unit + arithmetic logic unit)
- output
sequence of instructions stored inside computer
- built from predefined set of primite instructions:
- logic and arithmetic
- tests
- moving data
interpreter executes each instruction in order
turing: you can compute anything using 6 primitives, anything computable in one language is also doable in any other language
a language provides a set of primitive operations
primitives:
- english: words "boy"
- programming: strings, numbers, booleans, simple operations
syntax:
- english: sentence "boy is apple" => syntax correct (noun, verb, noun), but wrong semantics
- programming: expression
static semantics
- english: senctence "boy eats food" => syntax + semantics correct
errors:
- syntax
- semantics
- different meaning than what developer expected
program is a sequence of definitions and commands:
- definitions evaluated
- commands executed (instruct interpreter to do sth)

Objects in Python

program manipulates data objects
object has a type
type defines the things a program can do to them (x is human, so he can speak, eat etc.)
objects are scalar (can't get subdivided), non-scalar(has internal structure that can be accessed)
scalar objects: int, float, bool, NoneType
can convert (=cast) one type to another

Expressions

expressions are complex combinations of primitives
expressions and computations have values and meanings
expression = objects + operators
every expression has a value, which has a type
simple expression syntax: object operator object

Variables

assignment: bind variable to value
can re-bind variables using new assignment

02. Branching & Iteration

Strings

characters, letters, whitespace, digits
print()
input()

Conditionals

controls where program flows: if else

Loops

do stuff repeatedly
while: while sth is true, do this
for: for n times, do this

03. String Manipulations

strings are immutable
length: len
indexing: s[n]
slice: [::]

Algorithms

guess-and-check: guess a solution and check it
approximation: start with a guess and increment by some small value
bisection search: half interval each iteration, logsub2N

04. Abstraction, Decomposition, Functions

Abstraction

a TV is a blackbox
know the interface: input and output
input: connect other device to it that has data
blackbox converts input to output
Abstraction: do not need to know how TV works

=> programming: function specification , docstring

Why:

can't see details
don't need to see details
don't want to see details
hide implementation details

Decomposition

combine multiple TVs to display a big image
each TV takes input and produces output
Decomposition: different devices work together to achieve a goal

=> programming: code divided into modules => functions or classes